Previous packaging technologies include D. R. Paul and R. Clarke; Modeling of modified atmosphere packaging based on designs with a membrane and perforations; Journal of Membrane Science, 2002, 208 p. 269-283. This article discloses the use of CO2/O2 selective polymers as a method for improving the ability of packaged produce to breathe. This paper discloses the concentrations of CO2/O2, and water vapor in the packaging environment that matches the respiration rate of various produce.
V. V. Pethe, et al; (Oxygen and Carbon Dioxide Permeability of EAA/PEO Blends and Microlayers; Journal of Applied Polymer Science, 2008, 110, p. 1411-1419); disclose the use of various polyethylene oxide) and ethylene acrylic acid copolymers as materials that are viable for produce packaging applications. The highest pure gas CO2/O2 selectivity reported was 16.8 for the pure PEO matrix, whereas the highest CO2 permeability was 6.7 barrer.
Khemani et al., U.S. Pat. No. 7,297,394, Biodegradable Films and Sheets Suitable for use as Coatings, Wraps, and Packaging Materials discloses the use of a biodegradable polymer that has mechanical properties that are appropriate for food packaging. A water vapor transmission rate of at least about 80 g/m2/day is disclosed.
The control of atmospheric conditions inside produce packaging requires control of the transport rates of CO2, O2 and water vapor which is important in many packaging applications. Unfortunately, there are not many materials that satisfactorily demonstrate CO2, O2 and water permeabilities.
For instance, certain types of cut produce require dry environments to prevent decomposition. Other produce will become discolored if too much CO2 or O2 is present in the packaging environment.
Applications such as current produce packaging, the needs of the global produce shipping market are not being met. Fruits and vegetables continue to respire during transit, and they stay fresh longer if the atmospheric composition is tailored to their respiration rate. Current packaging materials do not have high CO2 or O2 permeabilities, and often suffocate the produce, which causes them to spoil quickly. It is desirable to design at least part of the packaging such that CO2 can escape from the packaging and O2 can enter around the produce.
As a result, there is a need for methods of maintaining the atmosphere in food packaging such that it extends product shelf life.